The influence of cannabis on driving

The results from a study of different doses of cannabis and the influence on driving and driving related skills are reported. The study required participants who were male, drivers and regular cannabis users to undertake a variety of different tasks. The participants were given cannabis to smoke, either in the form of a prepared grass-based cannabis cigarette or were asked to prepare a typical joint to smoke using supplied cannabis resin. The prepared 'grass' based cannabis cigarettes were supplied by NIDA (National Institute on Drug Abuse) and varied in active THC content to give a placebo, a low dose and a high dose. Each participant attended four test sessions where they were given a different cannabis dose, the dose ordering was fully randomised for the NIDA cigarettes. The participants drove the TRL simulator on a motorway, a 'figure of eight' and a dual carriageway with traffic light controlled junctions. Various measures of their driving skill were taken. They also took a test of their hazard perception and a compensatory tracking task. They also underwent sobriety testing 10-15 minutes after dosing and completed a mood questionnaire at different times during their test session. Three blood samples and four saliva samples were taken. On arrival urine was screened for polydrug use and a breathalyser test was administered to exclude recent alcohol consumption. The blood and saliva samples were analysed for different components of cannabis. (A)